Nonwoven webs have been used to produce absorbent articles useful, for example, as absorbent wipes for surface cleaning, as gas and liquid absorbent or filtration media, and as barrier materials for sound absorption. In some applications requiring high absorbency, it may be desirable to use a high porosity nonwoven article made up of high surface area fine sub-micrometer fibers. Fine sub-micrometer fibers, however, have a tendency to collapse or crush in handling, thereby decreasing the porosity and/or surface area available for absorption, while increasing the pressure drop of a fluid passing through the nonwoven article. For gas and liquid filtration applications in particular, it may be desirable to maintain a low pressure drop through the nonwoven article even while maintaining high absorbency.
Some current nonwoven articles use surface modifying agents to prevent fine sub-micrometer fibers from crushing. One example of this is the use of silicone oil in polypropylene sub-micrometer fibers to prevent cold welding. Using such surface modifying agents can cause complications, for example, when the nonwoven article is used as an absorbent wipe, or as a filtration medium. Some of these complications include leaching of the surface modifying agent over time, the propensity of the surface modifying agent to contaminate other surfaces or a gas or liquid medium passing through the nonwoven article, as well as the added cost of using a surface modifying agent solely to prevent crushing. While surface modifying agents may help promote crush recovery in a fine sub-micrometer fiber web, they do little to help with overall compression strength and Solidity under compressive load.